This invention relates in general to power assisted steering systems, such as are commonly used in vehicles. In particular, this invention relates to an improved mounting of a sensor within the power assist assembly for such a power assisted steering system.
Many vehicles in common use, such as automobiles, vans, and trucks, include a power assisted steering system for allowing a driver to pivot a pair of ground-engaging vehicle wheels about respective turning axes and, thus, control the direction of movement of the vehicle. A typical power assisted steering system includes a steering assembly and a power assist assembly. The steering assembly includes a steering wheel that is manually rotated by the driver to pivot the vehicle wheels about their respective turning axes. The power assist assembly is responsive to the amount of torque that is exerted by the driver to rotate the steering wheel for generating a force that assists in pivoting the vehicle wheels, thereby reducing the amount of torque that the driver would otherwise have to manually apply to the steering wheel.
The steering assembly commonly includes a rack and pinion mechanism that includes a steering shaft connected to the steering wheel for rotation therewith. The steering shaft has a helical pinion gear provided thereon that cooperates with a corresponding plurality of gear teeth provided on a transversely extending rack. The opposed ends of the rack are connected to the vehicle wheels such that linear movement of the rack causes pivoting movement of the vehicle wheels. When the steering wheel is rotated by the driver, the helical pinion gear provided on the steering shaft rotates relative to the rack. The cooperation of the helical pinion gear with the plurality of gear teeth provided on the rack causes the rack to move linearly relative to the steering shaft, resulting in pivoting movement of the vehicle wheels.
The power assist assembly typically includes a sensor that generates a signal that is representative of the amount of torque that is exerted by the driver to rotate the steering wheel and a hydraulic or electric actuator that is responsive to the sensor signal for selectively rotating an output shaft. In a column driven power assist assembly, the output shaft is connected through a gearing mechanism to the steering shaft. When the output shaft is rotated in response to the sensor signal, the gearing mechanism exerts a force on the steering shaft that assists in pivoting the vehicle wheels. To assist in more precisely controlling the operation of the motor, the power assist assembly further includes a sensor for detecting the speed and/or direction of the output shaft of motor.